montelukast sodium
Singulair

Available forms
Available by prescription only
Granules: 4-mg packets
Tablets: 10 mg
Tablets (chewable): 4 mg, 5 mg

Indications and dosages
 Prophylaxis and long-term treatment of asthma. Adults and adolescents: 10 mg P.O. once daily in the evening.
Children ages 6 to 14: 5 mg (chewable tablet) P.O. once daily in the evening.
Children ages 2 to 5: 4 mg (chewable tablet) P.O. once daily in the evening.
Children ages 12 to 23 months: 4 mg (granules) P.O. once daily in the evening.

Pharmacodynamics
Antasthmatic action: Montelukast causes inhibition of airway cysteinyl leukotriene receptors. Drug binds with high affinity and selectivity to the CysLT₁ (cysteinyl leukotriene) receptor, and inhibits the physiologic action of the cysteinyl leukotriene LTD₄. This receptor inhibition reduces early- and late-phase bronchoconstriction resulting from antigen challenge.

Pharmacokinetics
Absorption: Rapidly absorbed with mean oral bioavailability of 64%. For chewable tablet, mean oral bioavailability is 73%. The 4-mg granules and chewable tablets are bioavailable when fasting. High-fat meals decrease granules’ peak concentration by 35% and prolong time to peak from 1 to 3 hours to 3.5 to 9 hours.
Distribution: Minimally distributed to the tissues with a steady state volume of distribution of 8 to 11 L. Over 99% is bound to plasma proteins.
Metabolism: Extensively metabolized, but plasma levels of metabolites at therapeutic doses are undetectable. In vitro studies with human liver microsomes demonstrate metabolism involvement by cytochromes P-450 3A4 and 2C9.
Excretion: About 86% of an oral dose is metabolized and excreted in the feces, indicating drug and its metabolites are excreted almost exclusively in the bile. Half-life is 2 3/4 to 5 1/2 hours.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug or its components. Also contraindicated in patients with acute asthmatic attacks or status asthmaticus. Although airway function is improved in patients with known aspirin hypersensitivity, these patients should avoid aspirin and NSAIDs.

Interactions
Drug-drug. Phenobarbital, rifampin: Increases metabolism of drug. Monitor patient closely.

Adverse reactions
CNS: headache, dizziness, fatigue, fever, asthenia.
EENT: nasal congestion.
GI: dyspepsia, infectious gastroenteritis, abdominal pain.
Respiratory: cough, influenza.
Skin: rash.
Other: trauma, dental pain.

Effects on lab test results
• May increase ALT and AST levels.

Overdose and treatment
No information is available on treatment of drug overdose.
 Provide supportive measures for overdose such as removal of unabsorbed material from the GI tract and clinical monitoring.

Special considerations
• Although dose of inhaled corticosteroids may be reduced gradually, montelukast shouldn’t be abruptly substituted for inhaled or oral corticosteroids.
• Don’t use drug as monotherapy for management of exercise-induced bronchospasm.
• No added benefit is achieved with doses above 10 mg daily.
• Administer granules directly into the mouth, or mix with a teaspoon of cold or room-termperature applesauce, carrots, rice, or ice cream. Don’t open packet until ready to use; after opening, the full dose must be administered within 15 minutes. If mixed with food, don’t store excess for future use; discard any unused portion.
• Oral granules aren’t intended to be dissolved in liquid for administration. However, liquids may be taken after administration.
• Oral granules can be administered without regard to timing of meals.
Breast-feeding patients
• It isn’t known if drug appears in breast milk. Use cautiously in breast-feeding women.
Pediatric patients
• Safety and efficacy in children younger than age 12 months haven’t been established.
Geriatric patients
• No change in safety and effectiveness has been reported in geriatric patients.

Patient education
• Advise patient to take drug daily, even if asymptomatic, and to call if asthma isn’t well controlled.
• Warn patient that drug isn’t beneficial in acute asthma attacks or exercise-induced bronchospasm, and advise him to keep appropriate rescue medications available.
• Advise patient with known aspirin sensitivity not to take aspirin and NSAIDs.
• Warn patient with phenylketonuria that chewable tablet contains phenylalanine, a component of aspartame.
• Advise patients to seek medical attention if short-acting bronchodilators are needed more often than usual or prescribed.
• Give patient directions for mixing oral granules with applesauce, carrots, rice, or ice cream. Tell them to discard any unused portion.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use